Heater for hot isostatic pressing apparatus

A heater for a hot isostatic pressing apparatus for treating at least one workpiece in a high temperature and pressure gas atmosphere by application of heat and pressure, comprising:

• a stacked type heater having a plurality of heating element assemblies stacked one on another to form a vertical series of independently controllable heating zones;
• a generally cylindrical heater retaining cage having a plurality of annular graphitic members serving as girdle frames, a plurality of graphitic support columns serving as vertical frames, and a plurality of electric insulators connecting said annular members and support columns with each other and defining a series of divided sections around said heater retaining cage in each one of said heating zones;
• and
• a plurality of segmental graphitic heating elements supported in the respective divided sections of said heater retaining cage and extending between said plurality of insulators so as to form an independent heating circuit in each heating zone wherein said segmental heating elements are disposed in a space defined by a plurality of vertical planes containing inner and outer peripheries of said plurality of annular graphitic members.